The present invention relates to a basic logic circuit having a hot electron transistor (HET), a hot hole transistor, a hetero-junction transistor, a charge induction transistor or the like with multi-emitter.
In order to speed up the operation of a semiconductor integrated circuit, compound semiconductors composed of GaAs, InP, AlGaAs, InGaAsP and the like are used. This increase in speed is also achieved by miniaturizing circuit elements. However, there is a limit to such miniaturization and also, with higher integration, there is a delay caused by wiring in addition to the delay inherent to the circuit elements.
In the attempt to solve this problem, a multi-emitter transistor such as the hot electron transistor (HET) with multi-emitter shown in FIG. 12, has been developed (Japanese First Publication of Patent Application No. Hei4-96274).
A HET is obtained by growing the collector layer 2, the collector barrier layer 3, the base layer 4, the emitter barrier layers 5a to 5c and the emitter layers 6a to 6c on the semi-insulating substrate 1 by using a method such as molecular beam epitaxy (MBE), then vapor depositing the collector electrode 7 on the collector layer 2 and the emitter electrodes 8a, 8b and 8c on the emitter layers 6a, 6b and 6c respectively. For instance, the semi-insulating substrate 1 may be InP, the collector layer 2, the base layer 4 and the emitter layers 6a to 6c may be n-InGaAs, the collector barrier layer 3 may be i-In(AlGa)As, the emitter barrier layers 5a to 5c may be i-InAlAs and the electrodes 7, 8a, 8b and 8c may be Cr/Au.
As shown in FIG. 13A, when the collector electrode 7 of the multiple-emitter type HET is connected to the power supply line VCC via the load resistor 9 and a low or high level potential is imparted to each of the emitter electrodes 8a, 8b and 8c, the operation performed is as described below.
When the emitter electrodes 8a to 8c are at the same level, the potential for a free electron in the HET is as shown in FIG. 13B and the HET is set to OFF, collector electrode 7 being a high level. When the emitter electrodes 8a to 8c are not all at the same level and the potential difference between the high and low level exceeds a threshold level, namely exceeds the sum of the forward turn-on voltage and the reverse turn-on voltage between the emitter and the base, the potential for a free electron in the HET is as shown in FIG. 13C. An electron that has permeated the emitter barrier from the emitter layer of high level due to the tunnel effect becomes a so-called hot electron by its potential energy being converted into kinetic energy in the base layer. Most of the hot electrons run through the thin base layer at high speed to the collector and some of the electrons which are scattered and lost its kinetic energy are pulled through the other emitter barrier to another emitter layer of low level, making the potential of the base layer stable in the state as in FIG. 13C. The HET is turned ON and the collector electrode 7 become to the low level.
Because of this, development of other basic logic circuits with a reduced number of circuit elements and employing a multi-emitter transistor is eagerly awaited.